A known variable valve timing control device performing adjustable setting of a gas exchanging valve is disclosed in Japanese Unexamined Patent Application Publication 2009-515090 (hereinafter referred to as Patent reference 1). The variable valve timing control device disclosed in Patent reference 1 discloses a technology including a control valve inside a center screw that is connected to a camshaft, the technology including a check valve at a passage supplying hydraulic liquid (fluid) to the control valve.
In Patent reference 1, the check valve includes a closing body (a ball) that is biased in a closing direction by a spring element.
A technology in which a control piston is contained in a housing and in which a check valve preventing a backflow of an operating oil at a passage supplying the operating oil to the control piston is provided is disclosed in US2013-0118622A (hereinafter referred to as Patent reference 2).
In Patent reference 2, the check valve includes a plate having an opening, and a valve body supported by a plate-shaped elastic body so as to be able to close the opening.
A technology including a check valve having the same configuration as that of Patent reference 2 and a relief valve that are disposed in parallel to each other is disclosed in US2015-0300212A (hereinafter referred to as Patent reference 3).
Like an inside of a connecting bolt of the variable valve timing control device, in a case where the variable valve timing control device includes a valve unit that is coaxially disposed with a rotary axis, the distance between, one of an advanced-angle chamber and a retarded-angle chamber that are formed between a drive-side rotational body and a driven-side rotational body, and the valve unit may be reduced, and therefore, the responsiveness of the operation may be enhanced while reducing the pressure loss of a flow passage.
Furthermore, in the configuration in which the valve unit is coaxially disposed with the rotary axis, it is rational that a check valve is provided in the valve unit as disclosed in Patent references 1 to 3.
However, in the variable valve timing control device including the ball serving as the check valve disposed in Patent reference 1, the space for containing the ball and moving the ball in a release position is required, and therefore, the variable valve timing control device may be upsized. Furthermore, in the check valve having this configuration, because the ball is disposed at a center position of the flow passage, the pressure loss may occur by the contact of the fluid to the ball in a state where the check valve is open.
On the other hand, as disclosed in Patent references 2 and 3, the check valve including the plate being formed with the opening and the valve body closing the opening may be downsized. However, because the check valve is disposed at a position displaced from the rotary axis, fluid flowing in a passage in a state where the check valve is open may be easily in contact with a flow passage inner wall, and therefore, the pressure loss may occur.
A need thus exists for a variable valve timing control device which is not susceptible to the drawback mentioned above.